We know most native americans descend from people who moved from Asia into North America (and, it seems, at least some of them had west eurasian origins as well, and they all moved in either one, two or three migrations), and that place is really cold, so I suppose the first americans used clothes in some way similar to the typical clothes you see inuits wearing in historical pictures. When you go further south, however, you can see some tribes wearing less and less clothes, and in parts of South America no clothes at all.

Do we know when, in the process of going from current Alaska to the rest of the continent, the first tribes started using no clothes, and why?